1. Field of the Invention
The field of art to which this invention pertains includes shiftable change speed gear devices and particularly relates to a transmission, preferably of the constant-mesh gear type, having an interengageable jaw clutch shifting mechanism for substantially simplifying the shifting of the transmission and further having blocker means of simplified construction for improving the operation thereof.
2. Description of the Prior Art
In the design of constant-mesh gear transmissions, specifically heavy duty transmissions for use on trucks or the like, a longstanding problem has been the shifting of these transmissions through their various speed ratios. In most of these transmissions, the shifting process is relatively difficult or the shifting mechanism itself is comparatively complex. Continuing efforts are under way in the design of transmissions to improve not only the shifting method itself, but also to reduce the complexity of the shifting mechanism, to reduce its cost and to increase its reliability.
Nearly all of the previously-noted transmissions utilize synchronizer assemblies, of which many different types are known, with these synchronizer assemblies causing the speed of the jaw or toothed clutch members to be substantially synchronized prior to allowing their engagement during a shifting sequence from one speed ratio to another. While the use of synchronizer assemblies does ease the shifting operation, their use is, in many instances, somewhat undesirable since they not only increase mechanical complexity but also necessarily require additional space and add additional undesired weight and maintenance problems. Therefore, there has been a long existing need for improved heavy duty transmissions that can be readily shifted without the use of conventional synchronizers and yet permit quick, trouble-free shifts.
Examples of prior art shifting structures which operate without the use of conventional synchronizers include U.S. Pat. Nos. 3,799,002; 3,910,131; and 3,921,469. While all the structures shown in these patents appear to be readily workable, they all utilize resiliently yieldable shifting means, the use of which is entirely obviated in the structures of this invention.